Low temperature fluid

ABSTRACT

Low temperature heat transfer or functional fluid in the form of 1,1,2-trichloro-1,2,2-trifluoroethane, saturated with carbon dioxide, with or without the presence of solid carbon dioxide. The resulting fluid is a clear, low viscosity liquid at temperature down to -110*F and below, at ambient pressure, substantially below the freezing point of the above trichlorotrifluoroethane.

i United States Patent Nail 5] -()ct. 28, 1975 LOW TEMPERATURE FLUID 2,999,815 9/1961 Eisenman 252/67 2,999,816 9/1961 Bennett et a].

[75] Dmald Los Angeles 2,999,817 9/1961 Bower 252/67 [73] Assignee: McDonnell Douglas Corporation,

Long Beach, Ca]if Primary Examiner-Benjamin R. Padgett 22 M 23 1973 Assistant ExaminerJ0sephine Lloyd 1 I e Attorney, Agent, or FirmMax Geldin [211 App]. No.: 344,143

[57] ABSTRACT 52 us. c1.. 252/67; 252/69; 252/78 LOW temperature hfiat transfer or functional fluid in 51 1m. 01. C09K 5 00;c101v1 5/00 the form of 1,1,Z-IYiChIOYO-I,ll-trifluomethahe, [58] Field 61 Search 252/67, 78, 69 rated with Carbon dioxide, with or Without the P ence of solid carbon dioxide. The resulting fluid is a 5 References Cited clear, low viscosity liquid at temperature down to UNITED STATES PATENTS, 110F and below, at ambient pressure, substantially 2035 541 3/1936 Fl h 252,69 below the freezing point of the above trichlorotri- ClSC Bl 2,550,196 4/1951 Jones fluoroethane 2,590,542 3/1952 Jones 252/67 14 Claims, No Drawings LOW TEMPERATURE FLUID This invention relates to a low temperature fluid, and is particularly concerned with the provision of a refrigerant or low temperature heat transfer fluid or functional fluid comprising as the essential component, 1,1- ,2-trichloro-l,2,2-trifluoroethane, also referred to herein as trichlorotrifluoroethane, and marketed as Freon TF or Freon (113) by DuPont.

Various low temperature or solvent fluids have been developed containing mixtures of chlorinated fluorocarbons, particularly the Freons, such as trichlorotrifluoroethane, and other materials, and also mixtures of carbon dioxide with low temperature or cryogenic fluids. Thus, for example, US. Pat. No. 2,999,817 discloses an azeotropic mixture of 1,1,2-trichloro-l,2,2- trichloroethane and methylene chloride.

The compound 1,1 ,2-trich1orol ,2,2-trifluoroethane has also been disclosed as forming azeotropic mixtures with acetone (US. Pat. No. 2,999,815) and with methyl alcohol (US. Pat. No. 2,999,816). Mixtures of 1,1 ,2-trichloro-1 ,2,2-trifluoroethane with perfluorodimethylcyclobutane are disclosed in US. Pat. No. 3,578,597.

Carbon dioxide in the form of dry ice is also a wellknown refrigerant. This material has also been employed in combination with other materials and cryogenic fluids. Thus, US. Pat. No. 3,393,152 discloses a cryogenic liquid having a boiling temperature below about -300F at atmospheric pressure, in the form of liquid nitrogen containing finely divided solid carbon dioxide suspended in such liquid. As pointed out in the patent, cryogenic liquids having boiling temperatures substantially warmer than 300F have been found unsuitable because in such liquids the carbon dioxide particles tend to adhere to one another and form a solidified mass of solid carbon dioxide.

US. Pat. Nos. 2,550,196 and 2,590,542 disclose a composition comprising a block of solid carbon dioxide and frozen particles of a water solution of ethanol or methanol distributed throughout the block or cake of solid carbon dioxide. US. Pat. No. 2,290,532 discloses carbon dioxide dissolved in an amino-alcohol, as a refrigerant.

Neat or pure l,l,2-trichloro-l,2,2-trifluoroethane freezes at -31F (-35C) and hence, as such, cannot be employed as a refrigerant or functional fluid, and particularly as a low temperature heat transfer fluid, which is operable at temperatures below about 30F, that is, at temperatures ranging from about -30F down to about 120F, and lower. There are many applications, e.g. aircraft operations, where a heat transfer fluid or coolant is required which is operative and remains liquid at temperatures ranging from about OF down to about 120F, and lower.

It has been unexpectedly found, according to the present invention, that although 1,1,2-trichloro-l,2,2- trifluoroethane freezes at the above noted temperature of 3lF, l,l,2-trichloro-l,2,2-trifluoroethane saturated with carbon dioxide is a clear, low viscosity liquid at temperatures as low as about -108F to about 1 12F, and at even lower temperature, at ambient pressure. Such trichlorotrifluoroethane fluid saturated with carbon dioxide as noted above, has such advantageous low temperature properties, with or without the presence of excess solid carbon dioxide (i.e. dry ice).

It has been found from experience that a true depression of the freezing point of the trichlorotrifluoroethane occurs when this fluid in liquid form contains or is saturated with carbon dioxide at the temperature of use, rather than a super-cooling of the liquid. Thus, for example, the above trichlorotrifluoroethane has been frozen solid, and solid carbon dioxide (dry ice) placed on top of the trichlorotrifluoroethane. Within a few minutes the trichlorotrifluoroethane, though still well below its melting point, melts and a mixture of liquid l,1,2-trichloro-1,2,2-trifluoroethane saturated with carbon dioxide and containing suspended particles or chunks of solid dry ice, results.

The freezing point of liquid l,1,2-trichloro-l,2,2- trifluoroethane saturated with carbon dioxide gas has been found to be approximately l22F. The viscosity of such trichlorotrifluoroethane saturated with CO e.g. at -1 12F, is substantially less than the viscosity of water at room temperature.

If the trichlorotrifluoroethane fluid saturated with carbon dioxide according to the invention is subjected to pressure, as by pressurizing with CO a fluid is thus provided which is useful as a refrigerant, heat transfer fluid, or functional fluid at even lower temperatures than the above-noted approximately l22F freezing point for such CO -saturated fluid at ambient pressure.

In producing the novel fluid or liquid blend of the invention, carbon dioxide gas or solid carbon dioxide is introduced into the 1 ,l ,2-trichloro-1 ,2,2- trifluoroethane, preferably at least sufficient carbon dioxide either in gaseous or solid form being present to form a substantially saturated solution at the temperature of use. Thus, although pure l,l,2-trichloro-l,2,2- trifluoroethane has a freezing temperature of 3lF (35C) and solid carbon dioxide sublimes at l09F, 1,1 ,2-trichloro-l ,2,2-trifluoroethane saturated with carbon dioxide at 1l0F to 112F, or below, and down to about -122F, is a clear low viscosity liquid. Accordingly, such trichlorotrifluoroethane saturated with carbon dioxide, with or without the presence of excess carbon dioxide particles, remains liquid and is operative as a refrigerant, heat transfer medium, or functional fluid, over a highly desirable low temperature range of from about 30F down to about 1 20F, at ambient pressure, or lower if such fluid is under pressure. Further, since such fluid has a wide liquid range extending from low temperatures to elevated temperatures, the trichlorotrifluoroethane preferably saturated with CO liquid according to the invention can be employed as a circulatory heat transfer medium, hydraulic fluid or as a lubricant, particularly in the l20F to +87F range, especially in aircraft and space applications.

This is in contrast to the very low temperature cryogenic liquid useful at temperature only below about 300F disclosed in above-noted US. Pat. No. 3,393,152, and wherein it is necessary that solid carbon dioxide particles be suspended in the cryogenic liquid, for example, liquid nitrogen, and wherein it is noted that cryogenic liquids having boiling temperatures warmer than 300F are inoperative in combination with the carbon dioxide particles because the latter tend to adhere and form a solid mass.

At ambient pressure, by maintaining excess solid carbon dioxide present in the solution, this will maintain the solution saturated with carbon dioxide and gas is evolved from the solution until such time as all of the solid carbon dioxide has been consumed, thus maintaining a useful liquid at a particular low temperature down to a temperature as low as l20F, as for example, when the fluid is employed as a coolant or circulating heat transfer medium. Under pressure conditions in closed systems, the same or lower useful low temperature liquid range can be maintained as by suitably pressurizing the system with CO to maintain a substantially saturated solution.

It has been found significantly that other related chlorinated hydrocarbons and chlorinated fluorocarbons when saturated with carbon dioxide fail to produce useful low temperature liquids. Thus, for example, the following liquids failed in this respect:

a. l,l l -trichlorotrifluoroethane b. l, l ,2,2-tetrachloroethane c. chloroform d. l, l ,2,2-tetrachlorodifluoroethane e. l,l l -trichloroethane.

It is noted among the related halogenated hydrocarbons listed above, that, for example, l,l,ltrichloroethane has a freezing point of -33C, which is close to the 35C freezing point of l,l,2-trichloro- 1.2,2-trifluoroethane, yet the saturation of the former with carbon dioxide was ineffective in depressing the freezing point of this material, in contrast to the substantial suppression of the freezing point of l,l,2- trichloro-l ,2,2-trifluoroethane saturated with carbon dioxide, according to the invention.

An additional advantage of the present invention is that the trichlorotrifluoethane and CO components of the invention liquid are non-flammable, and hence, there is no danger of reaction with condensed liquid air or oxygen at extremely low temperatures.

The following examples further illustrate the invention.

EXAMPLE 1 About 390 grams of 1,1 ,2-trichloro-l ,2,2- trifluoroethane was slowly poured over about 285 grams of dry ice. There resulted a liquid consisting of l, l ,2-trichlorol ,2,2-trifluoroethane saturated with carbon dioxide and containing several pieces of dry ice. This liquid was prepared in a 2 liter dewar, and was then poured into a beaker and the total volume of the liquid was found to be about 350 ml, of which about 5 to of the total was solid dry ice. The temperature of the liquid was then found to be about 1 10F.

EXAMPLE 2 A container containing 66 grams of l,l,2-trichloro- 1,2,2-trifluoroethane was placed in a cooling bath consisting of liquid l,l,2'trichloro-l,2,2-trifluoroethane saturated at ambient pressure with carbon dioxide and containing solid crushed dry ice. The trichlorotrifluoroethane in the container froze solid. About 12 grams of solid CO was then placed in the container and the container with its contents was placed back in the l,l,2-trichloro-l ,2,2trifluoroethane-dry ice bath.

At this point the container held solid 1, l ,2-trichlorol,2,2-trifluoroethane at the bottom and solid CO powder at the top. After about 15 minutes, the container was withdrawn and the interface of the solid trichlorotrifluoroethane and solid dry ice was observed to be liquid. Bath temperature was -1l2F.

After another 2 hours in the cold bath, the contents at the bottom of the container were still solid, as were the contents in the top thereof, and there was approximately 15 ml of liquid at the interface. The container was then withdrawn from the cold bath and thus was supplied heat from the ambient room temperature atmosphere. In a few minutes the entire container was in liquid form except for a few pieces of dry ice, and rapidly evolving CO gas.

This example shows that no super cooling of the l,l 2-trichloro-l,2,2-trifluoroethane occurs upon saturation thereof with carbon dioxide, but rather an actual melting point suppression of the trichlorotrifluoroethane.

EXAMPLE 3 Additional 1 1 ,2-trichloro-l ,2,2-trifluoroethane was poured into the trichlorotrifluoroethane-dry ice bath used in Example 2 above. A few moments later, the temperature was found to be approximately -l 12F.

The clear liquid phase was then decanted. Volume of such liquid was 300 ml and it was clear, thinner than water and at a temperature of about --1 l2F. The solution in the absence of solid carbon dioxide was evolving gas rapidly. Such gas evolution could be stopped either by pressurizing the liquid or by chilling thereof.

EXAMPLE 4 The procedure of Example 1 was repeated, and the trichlorotrifluoroethane solution saturated with CO and containing particles of dry ice, and at ambient pressure, was then further cooled by immersion in a liquid nitrogen bath. The resulting solution was found to be maintained in liquid form down to about l20F.

Although it has been found preferable to maintain the solution of l,l,2-trichloro-l ,2,2-trifluoroethane and CO substantially saturated with respect to CO in order to obtain a liquid blend having as low a liquid temperature range as possible, less than saturated solutions of CO in the trichlorotrifluoroethane can be employed and still produce a liquid blend with a freezing point substantially lower than that of the pure trichlorotrifluoroethane. Thus, for example, liquid solutions of the trichlorotrifluoroethane having a concentration of CO ranging from saturation thereof down to, for example, about l0% saturation, may produce a liquid blend having a freezing point substantially below 3 1F. Where, for example, the solution is about saturated with CO the freezing point of such solution is below about -64F.

From the foregoing, it is seen that the invention affords a simple, economical means for transforming l,l- ,Z-trichloro-l,2,2-trifluoroethane from a liquid which has a relatively high melting point of 3lF to a fluid which has a wide liquid range at relatively low temperature ranging from about 30F to about 1 20F at ambient pressure, and which accordingly is particularly useful as a refrigerant, heat transfer medium or functional fluid, particularly within such low temperature range at ambient pressure. Such trichlorotrifluoroethane solution containing saturated CO thus has utility in aircraft and space application, particularly as a heat transfer fluid, as a functional or hudraulic fluid, and as a lubricant, and specifically including utility in low temperature circulating fluid systems such as used in environmental control systems for spacecraft and airborne electronic systems. The invention composition or fluid also has general utility as a refrigerant, e.g. in dry ice cold traps in laboratories in place of the conventional acetone, while being completely noninflammable, and as a thermometer fluid. The blend of trichlorotrifluoroethane preferably saturated with CO of the invention can be maintained either by having additional solid CO present in the solution, or by pressurization with CO While 1 have described particular embodiments of the invention for purposes of illustration, it will be understood that various changes and modifications can be made therein within the spirit of the invention, and the invention accordingly is not to be taken as limited except by the scope of the appended claims.

I claim:

1. A refrigerant, low temperature heat transfer fluid or functional fluid, consisting essentially of liquid 1,1,2- trichloro=l,2,2=trifluoroethane and carbon dioxide, said fluid having a concentration of CO ranging from about saturation down to about saturation.

2. A fluid as defined in claim 1, consisting essentially of l,l,2-trichloro-l,2,2-trifluoroethane saturated with carbon dioxide.

3. A fluid as defined in claim 2, additionally containing solid carbon dioxide in said fluid.

4. A fluid as defined in claim 2, said fluid remaining in liquid form when saturated with carbon dioxide at temperatore down to at least about =lO8F to about =11?? and at ambient pressure.

5. A fluid as defined in claim 3, said fluid remaining in liquid form when saturated with carbon dioxide at temperature down to at least about =l08F to about =1 12F at ambient pressure.

6. A fluid as defined in claim 2, said fluid having a freezing point of about -l22F and at ambient pressure.

7. A fluid as defined in claim 3, said fluid having a freezing point of about l22F at ambient pressure.

8. A fluid as defined in claim 2, said fluid remaining in liquid form when saturated with carbon dioxide at temperature down to at least about --lO8F to about -l 12F and at ambient pressure, said fluid having a freezing point of about -l22F at ambient pressure.

9. A fluid as defined in claim 3, said fluid remaining in liquid form when saturated with carbon dioxide at temperature down to at least about -l08F to about -l l2F and at ambient pressure, said liquid having a freezing point of about -l22F at ambient pressure.

10. A fluid as defined in claim 2, said fluid when pressurized having a freezing point below about l22F.

11. A fluid as defined in claim 3, said fluid when pressurized having a freezing point below about 122F.

12. A fluid as defined in claim 2, said fluid when pressurized with CO having a freezing point below about -l22F.

13. A fluid as defined in claim 3, said fluid when pressurized with CO having a freezing point below about 122F.

14. A fluid as defined in claim 1, said fluid having a concentration of C0,, ranging from about saturation down to about 50% saturation, said fluid having a freezing point ranging from about -l22F to less than about =64F. 

1. A REFRIGERANT, LOW TEMPERATURE HEAT TRANSFER FLUID OR FUNCTIONAL FLUID, CONSISTING ESSENTIALLY OF LIQID 1,1,2-TRICHLORO 1,2,2-TRIFLUORETHANE AND CARBON DIOXIDE SAIDFLUID HAVING A CONCENTRATION OF CO2 RANGING FROM ABOUT SATURATIO DOWN TO ABOUT 10% SATURATION.
 2. A fluid as defined in claim 1, consisting essentially of 1,1, 2-trichloro-1,2,2-trifluoroethane saturated with carbon dioxide.
 3. A fluid as defined in claim 2, additionally containing solid carbon dioxide in said fluid.
 4. A fluid as defined in claim 2, said fluid remaining in liquid form when saturated with carbon dioxide at temperatore down to at least about -108*F to about -112*F and at ambient pressure.
 5. A fluid as defined in claim 3, said fluid remaining in liquid form when saturated with carbon dioxide at temperature down to at least about -108*F to about -112*F at ambient pressure.
 6. A fluid as defined in claim 2, said fluid having a freezing point of about -122*F and at ambient pressure.
 7. A fluid as defined in claim 3, said fluid having a freezing point of about -122*F at ambient pressure.
 8. A fluid as defined in claim 2, said fluid remaining in liquid form when saturated with carbon dioxide at temperature down to at least about -108*F to about -112*F and at ambient pressure, said fluid having a freezing point of about -122*F at ambient pressure.
 9. A fluid as defined in claim 3, said fluid remaining in liquid form when saturated with carbon dioxide at temperature down to at least about -108*F to about -112*F and at ambient pressure, said liquid having a freezing point of about -122*F at ambient pressure.
 10. A fluid as defined in claim 2, said fluid when pressurized having a freezing point below about -122*F.
 11. A fluid as defined in claim 3, said fluid when pressurized having a freezing point below about -122*F.
 12. A fluid as defined in claim 2, said fluid when pressurized with CO2 having a freezing point below about -122*F.
 13. A fluid as defined in claim 3, said fluid when pressurized with CO2 having a freezing point below about -122*F.
 14. A fluid as defined in claim 1, said fluid having a concentration of CO2 ranging from about saturation down to about 50% saturation, said fluid having a freezing point ranging from about -122*F to less than about -64*F. 